1. Field of the Invention
The present invention relates to bisazo compounds, and more particularly to bisazo compounds useful as organic photoconductive materials in the field of electrophotography.
2. Discussion of Background
It is conventionally known that some azo compounds are useful as charge generating pigments when used in a charge generation layer of a two-layered type photoconductor, which is one embodiment of the electrophotographic photoconductors. The above-mentioned two-layered type photoconductor can be prepared by forming a charge generation layer and a charge transport layer successively on an electroconductive support. More specifically, the charge generation layer is formed on the support in such a manner that a charge generating pigment capable of generating charge carriers when exposed to light is vacuum-deposited on the support, or a solution of such a charge generating pigment or a dispersion prepared by dispersing finely-divided particles of the charge generating pigment in a resin solution is coated on the support. On the thus formed charge generation layer, the charge transport layer comprising a charge transporting material and a binder resin is overlaid. This charge transport layer has a function of effectively accepting and transporting the charge carriers generated in the charge generation layer.
As azo compounds used as the photoconductive materials in the photoconductor of the above-mentioned type, for example, benzidine-type bisazo compounds disclosed in Japanese Laid-Open Patent Applications 47-37543 and 52-55643, and stilbene-type bisazo compounds disclosed in Japanese Laid-Open Patent Application 52-8832 are conventionally known.
The two-layered photoconductors employing the above-mentioned conventional azo compounds, however, are poor in sensitivity, so that they are not suitable for use with a high-speed copying apparatus.